The Living Bridge Project: Local Flow Conditions at a Tidal Energy Conversion Installations at an Estuarine Bridge

The "Living Bridge Project" demonstrates an "Estuarine Bridge of the Future" at the Memorial Bridge in Portsmouth, NH. Researchers at the University of New Hampshire are analyzing data, developing models, and designing systems that combine smart user-centered infrastructure with emerging renewable energy systems and can lead to a more resilient and sustainable community. Structural health monitoring and environmental sensors are installed on the bridge and in the river below, and are powered by a locally available renewable resource, tidal energy. The project transformed Memorial Bridge, a vertical lift bridge over the tidal Piscataqua River connecting Portsmouth, NH and Kittery, ME, into a living laboratory for engineers, scientists, and the community.

Estuarine bridges could serve as ideal locations to deploy marine hydrokinetic (MHK) energy conversion systems. The hydrokinetic resource is often strongest at the narrow locations where bridges are usually located. The bridge piers can serve as supporting structure for both the bridge and hydrokinetic turbines, and the permitting process for MHK energy conversion can take advantage of the permitting work and studies required for bridge construction. The Memorial Bridge location in Great Bay Estuary is well-suited as a tidal energy test site, reaching tidal current speeds greater than 2.5 m/s during spring ebb tides.

In tidal estuaries the tidal current velocities can vary significantly in space and time. Measurements with two acoustic Doppler current profilers (ADCP), mounted on the bow and stern of the platform, were conducted followed by measurements with two acoustic Doppler velocimeters (ADV), mounted in different locations on the platform. The ADCP measurements indicated higher maximum current velocities and mean kinetic power density than found in the prior resource assessment measurements. The ADV measurements were motivated by the results of the ADCP. Turbulence time and length scales are generally consistent with estuary scales. The tidal flow turbulence characteristics, such as the size and occurrence of coherent structures, can influence the loading on the tidal turbine.

Data are available through the Living Bridge web site, https://livingbridge.unh.edu/

Project funding by NSF-PFI (grant IIP #1430260), FHWA, NHDOT and DOE.